1. Field of the Invention
This invention relates to a magnetic recording/reproducing apparatus for recording audio signals and video signals.
2. Description of the Prior Art
In a video tape recorder (VTR), transmission of a signal between a magnetic head and RF circuit is made through rotary transformers. In general and in a business-purpose VTR or the like, the RF circuit may be carried on the cylinder. Here, the RF circuit includes a recording amplifier, a reproducing amplifier, an equalizer and the like.
In the case of business-purpose VTR, simultaneous playback function and insert-editing function are essential in order to ensure the editing performance. As a result, a recording head, a reproducing head and an erasing head are required to be disposed on the cylinder. Here, the simultaneous playback function is a function to perform recording and reproduction simultaneously, which is necessary for confirming a recorded state or performing editing.
Referring to head-arrangement, It is general to dispose a plurality of heads at equal intervals peripherally of the cylinder in order to make sure of good head-to-tape contact and easy signal processing. Here, the head-to-tape contact indicates contact condition of head and tape. Also, disposing a plurality of heads at equal intervals peripherally of the cylinder is to arrange them equlangularly on the cylinder. In this case, however, when the tape winding angle is 180 degrees, two heads in pair or Ach (channel) head and Bch head are disposed so as to make an angle of 180 degrees with each other on the cylinder or diametrically oppositely disposed thereon.
Referring to a rotary transformer construction, a crosstalk measure between channels by providing short-rings between the recording/reproducing/erasing channels is taken thereby the rotary transformer forming a core of one body type. Conventional examples shown above can be clearly seen in a commercially available business-purpose video cassette recorder (VCR), for example, a D3 standard VCR or a D5 standard VCR, or in commercially available VCR, for example, a VHS standard VCR.
Recently, down-sizing a main body of a home-use VTR and even of business-purpose one has been required. In order to meet such requirement, it is necessary to make a diameter of the cylinder small (a small cylinder) and a recording track-pitch narrow (narrow track-pitch recording). However, with a VTR of having narrow track-pitch recording by the with a small cylinder, the following problems may be arisen as arise:    1. With the head arrangement and the rotary transformer construction as in the conventional examples, when a recording and reproducing simultaneously, a crosstalk of recording and erasing between the recording/erasing signals to and the reproduced signal is outstanding substantial, so that the simultaneous recording and reproduction becomes difficult;    2. When editing such as insert-editing, a narrowing trackwidth due to off-tracking generally occurs at a track of one track before of an editing start track and a track of one track after of an editing finish track. Here, the narrowing track indicates that the track not to be edited is erased by erasing or overwrite recording thereby to reduce an effective trackwidth.
However, in the case of the narrow track-pitch recording, as because the recording trackwidth is narrow originally, the narrowing track and the off-tracking as its cause when editing are required to be further reduced than would be made by the conventional ones, which is difficult to be attained at a conventional tracking accuracy.    3. When editing, in addition to the tracking as shown above, it is required to set an erase timing (erase starting point and erase finishing point) and a record timing (record starting point and record finishing point). Particularly, the erase timing is required to be set prior to renewal of an editing area by the recording head during head scanning.
With the VTR of narrow track-pitch recording by the small cylinder, however, the erase timing and the record timing are difficult to be set so as to satisfy the editing accuracy by applying such a conventional method that uses a PG signal from the cylinder (a rotational phase detecting signal of the cylinder), an FG signal from the motor (rotational frequency control signal of the motor), and a control signal from the linear track.    4. In order to prolong a recording time, it is general to increase a recording density or to narrow the recording track-pitch, which is being made for the home-use VTR previously. Even for the business-purpose VTR, it is required to set a long-time recording mode having narrow track-pitch other than a normal recording mode. If the recording track-pitch is narrowed in a long play mode, however, the cylinder is required to be newly provided with the head and the rotary transformer to be used for such narrowed track-pitch. The small cylinder is difficult to be additionally provided with the head and a rotary transformer channel to be used for the long play mode.